1. Field of the Invention
The present invention relates to polyesters prepared from an aromatic dicarboxylic acid component and a diol component. More particularly, the present invention relates to polyesters prepared from terephthalic acid or an ester derivative thereof and a diol component comprising 1,4 butanediol, which polyester exhibits improved impact properties.
2. Description of the Prior Art
Many different polyesters, modified to one extent or another, are known to the prior art. Polyethylene terephthalate (PET) is well known, and in view of its excellent physical properties and resistance to attack by chemicals is widely used commercially. Other polyesters such as polybutylene terephthalate (PBT) are also known, but not as widely accepted as PET.
One particular field of application for polyesters, and particularly polyethylene terephthalate, is the fiber industry. Therein, much of the modification of the polyesters is attempted in order to alter the spinning or mechanical properties of the polyesters, or the other properties important to films and fibers, e.g., such as improved dyeability. For example, see Muenster et al, U.S. Pat. No. 2,973,339, which discloses a process for the production of polyesters by reacting terephthalic acid or the dimethyl ester thereof with ethylene glycol and 5-30 mole percent (with respect to the terephthalic acid) of an aromatic glycol. The patent relates to a polyester useful in films and fibers.
Hrach et al, U.S. Pat. No. 3,651,016, discloses a process for the production of polyesters comprising reacting at least one lower alkyl ester of a dicarboxylic acid (including dimethyl terephthalate) with at least one diol selected from the group consisting of ethylene glycol, 1,4-butanediol, 1,4-(hydroxymethyl)-cyclohexane and 2,2'-bis(4'-beta-hydroxyethoxyphenyl)-propane. In Example 3 of the patent, there is disclosed the preparation of a polyester from a mixture of 200 parts terephthalic acid dimethyl ester, 150 parts ethylene glycol and 31.6 parts bisphenol A-diglycol ether. The result is an allegedly color stable polyester useful in forming films and filaments.
U.S. Pat. No. 4,067,850 issued to Kohler et al, discloses a process for the production of copolyesters by the transesterification of dimethyl terephthalate or the esterification of terephthalic acid with a glycol, such as ethylene glycol, in the presence of such quantity of bishydroxyethyl tetramethyl bisphenol A that the resulting polyester contains 4-15 weight percent of this bisphenol A in chemically co-condensed form. The filaments and fibers formed allegedly have improved dyeability properties.
Ohguchi et al, U.S. Pat. No. 4,377,682, discloses copolyesters formed from dicarboxylic acid components (which can include terephthalic acid and esters thereof) and an aliphatic glycol component containing mostly one or more glycols selected from ethylene glycol, tetramethylene glycol and 1,4-cyclohexane dimethanol, with a small portion of an additional glycol, and in addition small amounts of bisphenol A or bis-ethoxylated 2,2-bis(2,5-dimethyl-4-hydroxyphenyl)propane. The foregoing copolyesters are alleged to possess improved dyeability.
U.S. Pat. No. 3,972,852 issued to Inata et al, discloses a process of preparing aromatic polyesters from aromatic dicarboxylic acids or esters thereof (including terephthalic acid), diphenols and aliphatic dihydroxy compounds having 2 to 12 carbon atoms. The inclusion of the aliphatic dihydroxy compounds is said to permit the preparation of polyesters having a high deflection temperature under load as well as superior dimensional stability, thermal resistance and resistance to attack by chemicals.
See also Login, U.S. Pat. No. 4,263,370, which discloses graft polyesters prepared by grafting a monovinyl monomer to an unsaturated polyester which is the reaction product of at least one polycarboxylic acid reactant (including terephthalic acid and its esters) and at least on polyhydric alcohol reactant, with the provision that part of at least one of these reactants is alpha, beta-ethylenically unsaturated.
PBT is another known polyester, although generally not as widely employed a PET. A fire retardant PBT is known which comprises a brominated, ethoxylated bisphenol A component. Such polymers generally have a problem with color due to the bromine. The use of PBT in mechanical applications has been somewhat limited, however, as there is a need for a tougher PBT polyester, i.e., having improved impact properties. The prior art to date has not successfully addressed this problem. An improved, impact modified PBT type polymer would be of great commercial value to the industry.
It is an object of the present invention, therefore, to provide an impact modified polyester.
More particularly, it is an object of the present invention to provide an impact modified polybutylene terephthalate.
Another object of the present invention is to provide a polybutylene terephthalate copolyester having improved strength as well as improved impact toughness.
These and other objects, as well as the scope, nature and utilization of the invention, will be apparent to those skilled in the art from the following description, the Drawing and the appended claims.